WATER RELATIONS AND HYDRAULIC ARCHITECTURE OF WOODY HEMIEPIPHYTES

Several parameters related to the water relations of eight woody hemie piphytes with different photosynthetic pathways were studied in situ a nd in the laboratory on Barro Colorado Island, Panama, As a group, woo dy hemiepiphytes tended to have less conductive stems per unit leaf ar ea (lower k(L)) and invested less wood cross-section per unit leaf are a compared to free-standing trees, while their specific conductivity ( K-s)was significantly higher. Among hemiepiphytes, significant differe nces between C-3 and (Crassulacean Acid Metabolism) species in respect to leaf characteristics, transpiration rates, diel patterns of water flow through aerial roots, and in hydraulic architecture parameters. A verage transpiration rates of the two Clusia species (C-3-CAM) were lo wer by about an order of magnitude compared to the C, species, In an C , species, sap flow through aerial roots (F) closely followed transpir ation (E), whereas E and F were decoupled in time in the C-3-CAM speci es Clusia uvitana: considerable long-distance water flow occurred at n ight. The hydraulic efficiency of the other C-3-CAM species, C. minor, was the lowest of the five species investigated.